The use of containerized cargo units in shipping has increased in the past several years. The shipping of cargo in containerized units is highly efficient and allows a relatively large amount of cargo to be handled and shipped in a single package or cargo unit. The containerized cargo unit, therefore, minimizes the need to load and unload relatively small amounts of cargo and significantly decreases the handling times attributable thereto.
A typical containerized cargo unit is a rectangular box-type housing or container into which the cargo may be loaded and unloaded. The loaded containerized cargo unit may readily be moved from truck to railroad car to ship or to barge, as may be needed. Generally, a crane, forklift truck, or other lifting mechanism is used to lift the containerized cargo unit from a first mode of transportation to a second mode of transportation.
The upper rectangular surface of the containerized cargo unit contains, generally, four twistlock receiving members or corner fittings or female receptacles located at its four corners. A corner member is, generally, a plate structure having a particularly sized aperture designed to receive a twistlock and to permit rotation of the twistlock and its lugs for achieving locking or unlocking connection with the corner member. The twistlocks, or male members, extend from the lower frame of a fixed length or expandable length spreader. The spreader is a grapple suspended from a crane, or other lifting mechanism, which is aligned over the containerized cargo unit to be lifted. The spreader includes twistlocks which are to be aligned with the appropriate corner members for insertion therein.
Containerized cargo units come in any one of a number of sizes. Cargo units conforming to standards set by the International Organization for Standardization (ISO) and the American National Standards Institute (ANSI) have nominal container lengths from ten feet to forty feet but always have a nominal width of eighty-nine inches, measured from the center of one corner member to the center of the opposite corner member. An expandable spreader may be expanded or retracted to match the length required to align the twistlocks with the twistlock corner members at the four corners. Unfortunately, not all cargo units conform to the ISO-ANSI standards and this lack of uniformity may increase the time required to unload or load cargo units.
An example of a cargo unit not meeting ISO-ANSI standards is the Sealand system which has the center of the opening in the corner members at four-hundred and twenty inches in the longitudinal direction and ninety inches in the lateral direction.
Because of the differences in width or lateral spacing of the corner members of the Sealand and the ISO-ANSI system, it is necessary to either change the spreader or to use a spreader designed to accommodate both systems. Should the wrong spreader be used, then not all twistlocks will align with their respective corner members. Since twistlocks are, normally, rotated by means of hydraulic cylinders, improper positioning or misalignment of a twistlock may cause a malfunction such as jamming and a failure to release resulting in increased loading or unloading time.
Previous twistlocks designed to accommodate the ISO-ANSI system and the Sealand system, of which Loomis, U.S. Pat. No. 3,749,438, is an example, frequently jam because the torque on the twistlock caused by the operating or rotating means of the twistlock tends to force the twistlock to cant which may prevent the twistlock from entering into or releasing from the twistlock corner members.
Consequently, a new and improved twistlock operator having the capability of allowing the twistlock to accommodate various dimensional differences and to prevent malfunction of the twistlocks with the twistlock receiving members is necessary.